spi: dw: Use new spi_xfer_is_dma_mapped() helper

spi: dw: Use new spi_xfer_is_dma_mapped() helper

Replace a few lines of code by calling a spi_xfer_is_dma_mapped() helper.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
Tested-by: Neil Armstrong <neil.armstrong@linaro.org> # on SM8650-QRD
Link: https://lore.kernel.org/r/20240531194723.1761567-3-andriy.shevchenko@linux.intel.com
Tested-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Signed-off-by: Mark Brown <broonie@kernel.org>